Begi-s boost creep issues
 

Basically I have a begi s kit no intercooler with the gt2560 and am having some boost creep issues. The wastegate is rated for 6 psi, but I am seeing boost in upwards of 10-11 psi. Right now i have overboost protection on my ms set at 7psi, but this is only a temporary solution so i can drive the miata around town. I don't feel like removing the turbo to have it ported so is there anything simple i can do to combat the issue.

Could it be a clearance issue with the DP now allowing the wategate to open fully? This was an issue with some of their other DPs.

Call BEGI.

It seems to be hit or miss. Mine as well as my friends begi s kits are seeing boost creep, but i have heard other individuals kits holding at 6.

What are the numbers on the side of the actuator? I just want to make sure you have the correct one.
Stephanie

Read through this as well. Not exactly the same but some of the same issues might apply to you.
https://www.miataturbo.net/forum/sho...ht=boost+creep

the number on the wastegate is 480009-9

can anyone confirm if this is the correct wastegate

That is the 7 psi actuator. What downpipe do you have?
Stephanie

I have the standard downpipe included in the 1.6 s kit

Interesting. That should not be happening. Let me talk to Corky and I will get back with you. Can you shoot me an e-mail?
Thanks,
Stephanie

thanks and I will e-mail you as soon as possible

I'm looking into the 2560 kit myself. Keep us informed guys. :) Thanks.

Ditto - I have one on order.

same here too

The wastegate will need to be modified so when i have time i have to send bell engineering the exhaust housing from my turbo.

My BEGI-S kit (with a GT2560) should be ready this weekend and BEGI should have the turbine housing ported already. I'll take pictures of the wastegate area after I pick up the kit.

So, I think the DP is designed to bolt to the stock exhaust. I think I will install it initially with the stock system, then go get the 2.5"-3" system soon after. It would be interesting to do a before-after to look at several things, including boost curve behavior. I'll have MSI by then so I can log everything except horsepower. I could do something simple like a 3K-7K RPM timed run in 4th gear on a flat road.

I'll be happy to do a before-after HP run if someone else wants to pay for the dyno time :)

Its not a matter of porting the turbine housing, its a matter of the welded plate in the outlet flange that is not allowing the wastegate to open to its maximum potential.

Paul runs the same gt2560r. His only issue with the turbo was the small WG port. After porting it he had solid boost control. He had no actuator issues like some see with the BEGI divider plate. So in reality, the port is too small no matter what if you have any kind of free flowing intake and exhaust. The fact that some downpipes needed adjusting was a completely different issue that only some were affected by.

Zx-tex. I strongly suggest you take your turbine housing off and take the time to port it. As hard as you plan to drive your car, it will be more than worth while to you.

I exchanged e-mails with Corky a couple of times and he said the correct way to remedy the problem would be to port the wastegate, re-install the cat, or place a restrictor in the exhaust system somewhere. Installing the stock cat or placing a restrictor in my exhaust would be taking a step back so my only option is to port the wastegate. My boost creep issues are most likely linked to my test pipe and exhaust system. I know a few people running the kit with stock exhaust and the kit runs 6psi all day.

I don't think this one is the downpipe. The BEGi-S downpipe has more clearance than any ever made. The flange is actually two welded together and the internal flange is completely open. It is the same flange we have been using for 10 years.

Corky has decided that we are going to port all turbos in an effort to reduce the chance of over boost. Hopefully it will do the trick.
Stephanie

Should be ported already by Corky when I pick it up :)

OK I picked up the kit on Friday and it was indeed ported. Corky showed me where the modifications were done. Most of the material was removed (ported) in the area between the exhaust manifold flange and the wastegate area. The wastegate hole was opened up a bit as well.

Yes I know... TTIUWP... pictures coming soon...

yep

:useless:

I was unable to photograph some of the mods. But here is one. I would not recommend that you do this at home though.
Stephanie

My turbine housing looks EXACTLY like that one... because it is that one :)
Some more pictures. I processed these so the sharpness is much higher to exaggerate the details. The flange surface for example is smoother than how it looks here.

So thats whats meant by porting the wastegate. I thought it was opening the hole more.

This image was taken looking through the exit side of the wastegate, back towards the exhaust flange (looking upstream). The arrow points at the area where the material was removed. You can see the resulting arc shape in the casting.

The idea as explained to me by Corky is that the gases have a more direct path to the waste gate area. Loosely speaking, they do not have to change direction as quickly. The porting makes the change in direction of flow more gradual, thus resulting in better flow into the wastegate pocket.

^ Very interesting. I wouldnt have thought that would ever make a difference. I was constantly under the impression it was making the wastegate opening bigger. Seems to me there is some room to gain, how come they arent opened more?

Well I am guessing here, but based on the general understanding I have of flow (I am a Mech Engineer) as far as waste gate size goes
- There needs to be a certain amount of overlap between the waste gate valve face and the waste gate opening in order for it to seal properly. Leakage at low boost levels would mean slower spool times. The valve can only be so big in the housing due to space limitations, thus indirectly limiting the size of the port.
- If the opening is a lot larger, then the flow transition as the wastegate valve opens would be much more abrupt, possibly leading to instability in boost control. That is a guess though.

I'd be willing to say it is because there is more cost to do the extra work by the people making the cast pieces.

We manufacture cast products for our equipment and the more finishing that is done to the device at the end all costs us more $$$ overall. So there is a fine line between functional and works as specified vs. optimal and high performance. :)

Cheers,
Prospero

Yes, that too, good point. I did a little casting design work in my earlier days so I know enough to be dangerous. If you look at it, it would be hard to pull the core out of the casting with it tapered the way it is in the modified version, assuming it was sand cast, which it probably was. Of course there is always investment casting, which allows for flexibility in design, but that is more expensive for production pieces.

No doubt that it's a sand cast piece... and you're right about investment casting being the way to fly; just getting my engineers to keep from designing outside of what we built into the cast is the hard part. We cast a square today and they'll make an oval tomorrow. :giggle:

Cheers,
Prospero

Here is a good article on high-end, racing application turbos compared to production turbos. There is some discussion in there on turbine housing design.
http://www.mazdausa.com/MusaWeb/disp...ession4&bhcp=1

5-axis CNC machined compressor wheels... CHA-CHIIING! :eek5:

When going through my recent manufacturing magazine from SME I was suprised to see between 7 and 10 ads showing some kind of turbine/compressor wheel being machined by 5 axis mills. Very impressive to see the kind of work they can do. Thats also when you get into the realm of composite turbine housings and titanium internals.

Edit: That's funny, seen that article before, hadn't looked at it until after i typed this. I got to see one of those "elite" turbos, they were using it on a particular MSMS car at the time.

Yeah that makes a good ad for a mil considering that is a pretty complex profile to machine!

damn now I need to find some time to pull my turbo and send the exhaust housing back to bell

The porting shown in post #28 above is IDENTICAL to the porting recommended (required?) when installing catless downpipes/free flow exhausts on VF39-equipped Subaru's. The reason? To avoid/cure boost creep. Many have opened up the diameter of the port excessively with disastrous results. The technique shown and described above is how it should be done.

Scott

when Tim did mine he did both the path to the wastegate and the opening itself. i have no boost leak issues.

That does not make sense at all. A free flowing exhaust system should let the exhaust gases exit more quickly = less boost creep.
I had the same problem with the Begi S. Corky tried to help me and said that he would check one of his own gt2554 and call me back. He never did, I ended up porting the turbo myself as I cant afford to not having a running car for a month waiting for them to port it.
Now that it's ported it wont boost creep as much, only when it's cold weather

you wouldn'd agree that free-er flowing exhaust allows the car to build more boost?

it allows the exhaust gases to exit more quickly out of both the wastegate AND the exhaust housing. but since they are not equally restrictive the whole path of less resistance comes into play. air will flow more through the turbo than through the wastegate since the wastegate passage is more restrictive therefor building more boost

the unrestricted exhaust further exaggerates the difference in how restrictive the waste gate and exhaust outlet are.

:nuts:

fixed it for you

Porting the wastegate is not something we recommend you do at home. Not only does the casting get drilled out, Corky said there is a small hole drilled elsewhere.

We are more than happy to port a wastegate for anyone (regardless of who it was purchased from) at no charge. Just send us your turbo and we can send it back within a day or two. A pain to do, yes, but safer in the long run.
Stephanie

^ any turbo?

Garrett, with an internal wastegate.
Stepahnie

hmm......with an offer like that, i'll have to keep an eye on any signs of boost creep with my new begi-s 2554.

Wow. that's an awesome offer buy BEGi. another reason I am placing my order for the S tomorrow through Shore Motorsports.

i need money to order my kit from them...... makes me not happy

Yeah. BEGI for the win!

Had boost creep initially - ended up shortening the dp just a bit (1") and it went away :-) This is on a high flow 2.5" cat back.

order has been placed. eta 2 weeks due to turbo shortage or backlog(because of porting?)

At what cost? my T3 doesn't see less than 13psi at redline with your manifold and DP and Jason's 3" catback. :naughty: I planned on doing it myself with a die-grinder, but i cant refuse this offer... I still need your water-bypass kit, so i might as well get it sent back with my order.

Shipping cost only.
Stephanie

Amazing service!

This does work but then there is a chance that when you do actually want to turn up the boost the flapper will blow open. This has been proven time and again with larger flappers on MHI turbos. But we're talking about 15+ psi and over 300hp so I'm not sure what bearing this has in this application.

Good point. As most of you probably know, force is surface area times pressure, and area goes up with the square of the radius. Doubling the diameter for example means quadrupling the area. I'm not saying of course that anyone would double the size of the wastegate, just using that for illustration. But the point is a small change in the wastegate diameter has a potentially strong effect on the force required to hold the valve closed, thus probably requiring a stronger spring in the wastegate actuator to compensate.

OK that is enough technobabble for a Friday night. Time for a beer.

Synasthetic,

You're on a turbo website. Guys building, installing, modifying there own stuff. Of course there are going to be issues. Take a Greddy kit and push it to 18psi and stuff will break.

The BEGI S system is basically brand new. BEGI saw the boost creep problem and are now taking steps to correct it - porting the WG.

There are hundreds of guys running FM, BEGI, custom and DIY kits for a long time without significant issues. There are lots of guys here that have great running systems with little or no issues. The thing with DIYers is lots of the problems wouldn't be significant if we weren't always looking for ways to get more power, more efficiency and push closer to the limits of the engine. You take a small 4 banger and double or triple the horsepower there are going to be occasional problems. Lots of people also can't pay for dyno time for proper tuning.

Check out the websites, if there are any, on the engine swaps. I'm sure everything isn't all rosy there either.

Enough trying to convince the Newb not to give up on turbos. Just ban him.

i had a swapped civic once, it sucked... never ran the same, always had stupid little issues
have a boosted miata now, and it runs like stock, only faster...

turbo - my replacement for displacement

No boost creep here at 8psi!